1. Field of the Invention
The present invention relates to a manually operated control valve on a pneumatically operated device, with an in particular horizontally positioned control shaft rotatable in one or the other direction against a rising resistance out of a neutral central position and with an operating member extending from the control shaft to floor or ground height.
2. Prior Art
Such control valves are particularly used on pneumatic lifting equipment operated by two control cables fixed to a rocker, the latter being fixed to the control shaft or spindle of the control valve. By pulling on one or the other cable, it is possible to controllably select the operating mode "raise" or "lower". Such cable controls are always required if the pneumatically operated equipment is outside the reach of the operator, i.e. is for example fixed to a roof beam or to a monorail facility.
In the case of a monorail mounting or gallows-like cantilever brackets, apart from the raising and lowering operation, it is often desirable to have a local displacement for which the lifting appliance is drawn on rollers along the monorail or along the brackets. This displacement is carried out manually with the aid of a cable which hangs from the pneumatic appliance and which is pulled or dragged in safety.
Such a cable control suffers from certain disadvantages. Despite a certain spacing being provided, there is a risk of the two operating cables becoming entangled. Moreover, in some cases operation can be made difficult or impossible if e.g. a pneumatic lifting appliance is used for a horizontal dragging movement or for a horizontally directed adjusting or positioning work. The cables then hang down vertically, but operation by merely pulling is made difficult or even impossible. Therefore, attempts have been made to replace the aforementioned cable control by bevel gears permitting the vertical bending of the control shaft on operating the pivot pin about the horizontal axis. A rod is provided on the now vertical operating member, which is attached to one bevel gear by means of a cardan joint and permits an actuation of the pneumatically operated equipment as a result of a rotary movement.
It has been found that the aforementioned difficulties cannot be overcome by bevel gears in the case of a horizontal action direction, e.g. of pneumatically operated lifting equipment. Thus, in such operating positions, the cardan joint virtually ceases to have any effect, so that a swinging rod brings about the operation of the pneumatically operated equipment. Thus, this solution cannot be satisfactory for safety reasons. In addition, the bevel gears must be given an extremely robust construction due to the tractive forces applied via the rod and this leads to correspondingly high costs.